Everyday Math Skills Workbooks series - Simply Math - My ERC
Everyday Math Skills Workbooks series - Simply Math - My ERC
Everyday Math Skills Workbooks series - Simply Math - My ERC
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<strong>Simply</strong> <strong>Math</strong> Booklet<br />
The Basic <strong>Skills</strong><br />
An estimate can sometimes be improved. If the difference of 645 - 450 were<br />
estimated, we would round 645 to 600 and 450 to 500. The estimate would be 600<br />
– 500 or 100. One number was rounded down and the other was rounded up.<br />
The number 645 was rounded down by 45 and 450 was rounded up by 50.<br />
Adding 45 + 50 gives 95, which rounds to 100. Therefore, a better estimate would<br />
be 200. The actual difference is 195.<br />
How can you improve the estimate<br />
1. Round each term that will be subtracted.<br />
2. Subtract the rounded numbers.<br />
3. If one is rounded down and the other up see if the amount of rounding is<br />
more than 50. If it is, add 100 to or subtract 100 from the estimate.<br />
4. If both numbers are rounded down or both are rounded up, a closer<br />
estimate will not be produced by this method.<br />
For example: Estimate 955 – 325<br />
1. Round each term. 1000 – 300<br />
2. Subtract. 700<br />
3. Add 55 + 25 = 80 (more than 50)<br />
Subtract 100. 700 – 100 = 600<br />
4. Estimation: 600<br />
5. Actual answer: 630<br />
NWT Literacy Council<br />
15 15<br />
<strong>Simply</strong> <strong>Math</strong> Workbook
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